1. Field of the Invention
This invention relates to a method for forming a monomolecular adsorption film of a material having diacetylene bonds on a substrate by chemical adsorption and also to a method for forming built-up films of monomolecular layers wherein diacetylene bonds or polydiacetylene bonds are formed in the films. These films have wide utility as a conductive or insulating film in the fields of semiconductive industries.
2. Description of the Prior Art
Attention has been heretofore directed to polydiacetylene materials since they have a very long conjugated polydiacetylene bond in the molecule and exhibit a non-linear optical effect and electric conductivity. These materials are considered to have utility as a functional material. For obtaining these polymers from monomer molecules in the form of crystals which are more functional, studies have been made using the Langmuir-Blodgett technique or vacuum deposition technique.
In general, in order to impart good optical properties to polydiacetylene material, it is necessary that the polymer have a very long polydiacetylene bond. When the Langmuir-Blodgett technique is used, the molecular orientation and density of the monomer can be arbitrarily controlled. This is advantageous in that the reactivity of the monomer by irradiation of actinic light ca be easily controlled. However, when the monomolecular film of the polydiacetylene is formed by the technique, the diacetylene monomer on the water surface in the Langmuir-Blodgett trough is crystallized to form defects in spite of the surface pressure from outside. This leads to the problem that the conjugation length after the polymerization is limited.
On the other hand, the formation of polydiacetylene by the vacuum deposition technique is advantageous in that the film thickness can be appropriately controlled. However, the drawback of the technique is that when heated excessively, the monomer decomposes.
In U.S. Pat. No. 4,673,474, there is mentioned chemical adsorption but this patent does not particularly set out the type of material to be adsorbed and adsorption conditions for such a material.